In a computer system having a display device, the interactive operation of the system by a user is typically based on visual feedback from displayed information on the display. For example, a user may be required to repetitively choose software options displayed on the display, or may desire to input data in graphics format (e.g., drawing images on the display) into the computer system.
The advances in computer interface technologies have led to the use of control signal generating devices as interface devices to effect such interactive operation. The devices control the position and movement of a cursor or a pointer on the screen of a computer controlled display. The control signals generated by these devices include coordinate signals for a selected position of the cursor on the display. The coordinate signals are used to drive display circuits of the display device to control the movement of the cursor from its current position in the display to the selected position.
One prior type of such control signal generating device is commonly referred to as a "mouse." One example of the mouse is described in U.S. Pat. No. 4,464,652, issued in August 1984. The mouse is often used to control the position of a cursor on the computer's display screen to thereby position the cursor over an object to select the object for an action or otherwise to instruct the computer to perform an operation. Another prior type of such control signal generating device is commonly referred to as "joystick."
While the use of these devices for such interactive operation is very effective and very "user friendly," it has been found that disadvantages are associated with such prior types of devices.
One prior disadvantage associated is that when using each of these devices, the entire hand has to be used to operate these devices. The user must stop his or her hand operation on a keyboard or other type of input devices and move his or her hand from the keyboard to grasp the mouse or joystick. It sometimes also requires that the user's eyes be shifted from the display to aid in the grasping of the device. In many applications (e.g., word processing), the operation of such device results in a substantial loss in convenience and efficiency due to the diversion of the user's attention from the display.
Another prior disadvantage associated with these devices is that when a user wishes to place the cursor at a desired spot on the display, the user has to operate the control signal generating device in order to move the cursor from its present position to the desired position on the display. Therefore, the device provides a less natural, non-coincident input path for the user.
One prior approach to solving these problems is to develop a control signal generating device that can be activated by a finger press or finger touch. One example of such device is described in U.S. Pat. No. 4,692,756, issued on Sep. 8, 1987. This prior signal generating device includes a plane window area in which an actuating knob is located. The knob can be moved by a finger within the window area. The movement of the knob within the window area results in the production of coordinate control signals which represent the coordinates of the position of the knob. The control signals are then used to determine the position of the cursor on the display.
Another prior approach to overcoming these problems is to develop a press/touch sensitive control signal generating device. The device is typically mounted on the frame of the display screen. The user's finger touch/press at a spot on the device causes the device to produce control signals representing the position of the finger touch/press spot. The control signals are thus used to determine the selected position of the cursor on the display and place the cursor onto the selected position on the display. The touch/press sensitive device provides more natural and coincident input path to the computer.
One disadvantage of the finger/press touch type of prior devices is that these devices were designed to allow the user to move the cursor on the display in two-dimensional representation. The technological developments in computer graphics, however, have made it possible for objects to be displayed in three-dimensional representation, for example in wireframe, solid and/or shaded forms on the display. Therefore, it is desirable to develop a touch/press type of control signal generating device that allows three-dimensional control signal input.
One prior solution is described by C. F. Herot, et al. in an article entitled "One-Point Touch Input of Vector Information for Computer Displays," Computer Graphics, Vol. 12, No. 3, August 1978. In that article, a three-dimensional pressure/touch sensitive digitizer is disclosed in which the X-Y input corresponds to the location of a press input on the device, and the Z input corresponds the force normal to the device. The device includes a sheet of clear glass mounted on two adjacent edges. The device is secured to a screen of the display by means of four octagonal rings. The device also employs eight semiconductor strain gauges, with two secured on a mounting ring. All forces exerted on the device are transmitted to the rings, thus causing deformations which in turn flex the strain gauges secured to them.
One disadvantage of this three-dimensional pressure/touch device is that the thickness, and hence flexibility of these rings is critical to the sensitivity of the gauges' measurements. Because the rings are designed to accommodate subtle pressures, high finger pressures cannot be precisely measured. Moreover, a vibration from a nearby source may trigger the gauges, thus resulting in a false input.